The uncontrolled blaze pressed in on the Canadian oil city of Fort McMurray after more than 80,000 people were forced to run for their lives. Authorities warned that the next 24 hours would be critical for the city's survival.

"Pipelines in the region are being shut as a precaution, while output at facilities in the area are being disrupted," said Matt Smith at ClipperData.

"Numbers are being bantered around, with estimates as high as 800,000 barrels per day for how much Canadian production could be offline," he said.

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West Texas Intermediate (WTI) for delivery in June ended at US$44.32 a barrel, up 54 cents, on the New York Mercantile Exchange. The key US futures contract rose as high as US$46.07, a level last reached in November, before pulling back.